1. Field of the Invention
This invention resides in the field of automated analyzers for biological samples.
2. Description of the Prior Art
The analysis of biological fluids such as blood, urine, tissue extracts, and the like is often done on a large number of samples and by methods that involve comparisons among samples and against standards. A high degree of precision is needed, particularly when the sample contains a variety of competing species that can interfere with obtaining proper analytical results. Automated analyzers are well adapted to use on large numbers of samples and to the performance of analyses in a repetitive and uniform manner. In addition to providing convenience and economy, automated analyzers eliminate the variations that frequently occur when analyses are performed manually, and particularly by different individuals.
One of the difficulties with automated systems is the need to remove debris from the samples before the samples enter the critical analytical components such as chromatographic columns and detectors. This is particularly true for blood samples, which are first treated by hemolysis to liberate the species of interest and the proteins in general before entering the analytical system. The types of sample debris that are present in the hemolysate include cell wall fragments and other particulates as well as lipids. All such debris enters the system during the sample preparation and handling.
The removal of sample debris is particularly important in automated systems that utilize high-pressure units such as high-performance liquid chromatography (HPLC) to separate the sample components for purposes of identification and quantification and those that contain switching valves that are used in the automated sequences of sample handling. Once the contamination in these components reaches a degree where the analysis is impaired, the analyzer must be shut down and opened so that the contaminated part, whether it be an analytical column or an internal valve, can be removed and either cleaned or replaced. The time consumed in performing these tasks and the lost usage time of the instrument can be costly. Also, the possibility of errors occurring before the shutdown casts uncertainty on the reliability of the instrument and on the accuracy of the analyses already performed.